Bulk process gas purification systems

ABSTRACT

Described are bulk process gas purification systems and related methods, including systems that are adapted to use a volume of gas at an exterior surface of a vessel, e.g., a flow of the gas, to control a temperature of the vessel interior during a recharging step, during a cooling step that follows a recharging step, or both.

FIELD OF THE DISCLOSURE

This disclosure relates to bulk process gas purification systems andrelated methods, including systems that are adapted to use a volume ofgas at an exterior surface of a vessel, e.g., a flow of the gas, tocontrol a temperature of the vessel interior during a recharging step,during a cooling step that follows a recharging step, or both.

BACKGROUND

In the electronics industry, high purity specialty gases such ashydrogen, argon, helium, oxygen, carbon dioxide, nitrogen, ammonia(NH₃), and extra clean dry air are required for many operations and aregenerally obtained in either high purity cylinder form or from bulk gassources which are purified at a point of use, such as at a semiconductorfabrication plant. High purity cylinder sources are capable of providingrequired high levels of purity for the gaseous raw materials, but maynot be convenient or cost effective where very large volumes of gas areneeded on a continuous basis at multiple points of use within amanufacturing facility.

As an alternative to cylinder sources, bulk source specialty gases maybe used for certain types of gaseous raw materials. Bulk sourcespecialty gases may be stored in pressurized or liquefied form in tankcars, tank trucks, large scale on-site storage, or the like, or may besourced from compressors located at or near a point of use. Bulk sourcespecialty gases can be provided in large volumes, but may need to beprocessed to a substantial degree for the gas to meet required highstandards of purity.

When bulk source specialty gases are used, an on-site purificationsystem capable of purifying very large volumes of a specialty gas on acontinuous basis may be used to achieve the necessary levels of highpurity and high volume. Such a purification system may operate centrallywithin a manufacturing plant to deliver a gaseous raw material tomultiple destinations within the plant, which may include multiple workspaces and multiple manufacturing apparatus (tools). The use of acentral purification system may result in efficiency and cost savingsrelative to other modes of providing a gaseous raw material.

Typical on-site purification systems include at least one, but moretypically at least two, purification vessels that contain a purificationmedia (e.g., filter media) for purifying a specific type of bulk processgas. In a purification process of a typical on-site purification system,a flow of bulk process gas enters a purification vessel through a vesselinlet, passes through the purification media that is contained at theinterior of the vessel, and exits the vessel through a vessel outlet inthe form of purified bulk process gas that then distributed to one ormultiple different destinations within a manufacturing facility. Thepurification media may include filter media such as an adsorbent thatsequesters impurities such as water (humidity), hydrocarbons,microscopic particulates, or other contaminants. The purificationprocess is operated at a purification temperature. In some systems, atypical range of purification temperatures is from 10 degrees Celsius to60 degrees Celsius. Excessively high purification temperatures should beavoided, as too high of a temperature may reduce the ability ofpurification media to sequester contaminants or even cause purificationmedia to release previously sequestered contaminants.

To maintain effectiveness, the purification media within thepurification vessel must be periodically regenerated. In a regenerationprocess, valves at the vessel inlet and outlet are closed to take thevessel off-line (i.e., closed to apparatus to which the vessel suppliesa gaseous raw material) and to allow a regeneration gas heated to aregeneration gas temperature to be passed through the filter mediawithin the purification vessel. Typically, to prevent contamination ofthe filter media in the vessel, the regeneration gas is a purified gassuch as previously-purified bulk process gas, e.g., bulk process gasthat has been already purified (e.g., using the same vessel or acounterpart vessel) and optionally stored. Alternately, the regenerationgas can be a gas other than previously-purified bulk process gas; if so,the regeneration gas must be of a high purity such that it contributesto removal of contaminants. Typical regeneration gas temperatures are inexcess of 60 degrees Celsius when passing through the vessel, often wellin excess of 60 degrees Celsius, and may be in the range from 250 to 450degrees Celsius.

SUMMARY

A purification vessel, after a regeneration step, can be brought back online and used for continued manufacturing only after the vessel and itscontained filter media have cooled to a useful operating temperature. Insome systems, the regeneration process includes a regeneration stepfollowed by a cooling step during which a cooling gas at a cooling gastemperature (below the regeneration temperature) is passed through thefilter medium within the purification vessel to remove heat from thefilter medium and reduce the temperature of the filter medium. Thecooling gas can be a pure gas, such as purified bulk process gas, whichmay be purified bulk process gas that was previously purified and storedor purified bulk process gas sourced from another vessel. Typicalcooling gas temperatures may be from 10 degrees Celsius and 60 degreesCelsius.

Typical on-site purification systems comprise at least two purificationvessels and accompanying conduits and valves to allow one vessel tocontinue in operation while the other is regenerated.

In one aspect, the invention relates to a bulk process gas purifiersystem. The system includes a purifier that includes a vessel having avessel interior that contains purification media. The system alsoincludes an enclosure that encloses the vessel and defines an interspacethat is inside the enclosure and external to the vessel. The enclosureincludes air circulating passages to allow: a flow of ambient gas intothe interspace at a positive input pressure; non-convective circulationof the ambient gas within the interspace; and flow of circulated ambientgas from the interspace to an exterior of the enclosure at a positiveoutlet pressure. The air circulating passages include: an enclosureinlet that allows a flow of ambient gas at a positive input pressurefrom the exterior of the enclosure into the interspace; an enclosureoutlet that allows a flow of ambient gas at a positive output pressurefrom the interspace to an exterior of the enclosure; and a bulk processgas circulating system adapted to cause the bulk process gas to flowinto the vessel interior, through the purification media, and out of thevessel interior.

In another aspect the invention relates to a method of using andregenerating purification media of a bulk process gas purifier system asdescribed herein. The method includes: passing bulk process gas throughthe purification media at purification temperature to cause impuritiesin the bulk process gas to be removed by the purification media, and toproduce purified bulk process gas having a reduced level of theimpurities; after impurities have collected in the purification media,regenerating the purification media by passing regeneration gas having aregeneration gas temperature through the purification media, whereby theregeneration gas heats the purification media to a regenerationtemperature to cause collected impurities to be removed from thepurification media and flow from the vessel with the regeneration gas;after regenerating the purification media, cooling the purificationmedia by passing cooling gas, at a cooling gas temperature that is belowthe regeneration temperature, through the purification media to reducethe temperature of the purification media. During cooling, a flow ofambient air is passed through the interspace at an ambient air coolingtemperature that is below 60 degrees Celsius, with the ambient air:passing from a location exterior to the system enclosure, through theenclosure inlet, and into the interspace; circulating within theinterspace in a non-convective manner; and passing from the interspacethrough the enclosure outlet to a location exterior to the enclosure.

The preceding summary of the present disclosure is not intended todescribe each embodiment of the present invention. The details of one ormore embodiments of the invention are also set forth in the descriptionbelow. Other features, objects, and advantages of the invention will beapparent from the description and from the claims.

All scientific and technical terms used herein have meanings commonlyused in the art unless otherwise specified.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” encompass embodiments having pluralreferents, unless the content clearly dictates otherwise.

As used in this specification and the appended claims, the term “or” isgenerally employed in its sense including “and/or” unless the contentclearly dictates otherwise.

As used herein, “have”, “having”, “include”, “including”, “comprise”,“comprising” or the like are used in their open ended sense, andgenerally mean “including, but not limited to.” It will be understoodthat the terms “consisting of” and “consisting essentially of” aresubsumed in the term “comprising,” and the like.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic depiction of one embodiment of the use of gaspurification systems according to the present disclosure in asemiconductor manufacturing plant.

FIG. 2 is a schematic depiction of a portion of one embodiment of a gaspurification system according to the present disclosure.

FIGS. 3A, 3B, and 3C, are schematic depictions of a portion of oneembodiment of a gas purification system during the purification process,the regeneration step of the regeneration process, and the cooling stepof the regeneration process, respectively.

DETAILED DESCRIPTION

The following description relates to methods and apparatus that enable afaster cooling step in a regeneration process of a purification vesselthat includes a regeneration step during which the purification vesseland its contents of filter media are heated, followed by a cooling stepduring which the purification vessel and its contents are cooled.

A faster regeneration process results in a number of advantages. Aregeneration process consumes an amount of regeneration gas during theregeneration step and an amount of cooling gas in the cooling step. Eachof these gases is typically a purified bulk process gas that has beenpreviously purified by the purification system being regenerated (or acounterpart), and would otherwise be used for manufacturing operations.Reducing the amount of time for performing a cooling step of aregeneration process conserves cooling gas by reducing the total amountof cooling gas that is consumed during the cooling step. Also, becausethe purification vessel must be off-line during the regenerationprocess, including the cooling step, the peak capacity of a dual vesselpurification system is halved. A faster regeneration process (includinga cooling step) reduces this disadvantage. During regeneration, thesecurity offered by the redundancy of a dual vessel system is lost. Afaster regeneration process reduces this disadvantage.

Methods and systems of the present disclosure involve a cooling stepthat follows a regeneration step, with the cooling step using coolinggas passed through a purification vessel to reduce a temperature offilter media contained at the interior of the vessel. In addition to theflow of cooling gas at the vessel interior, the methods and systems alsoinvolve added control of the vessel temperature during the cooling stepby using a non-convective flow of gas at an exterior of the vessel.

According to the invention, the vessel is contained in an enclosure thatis a substantially closed structure that includes sidewalls, a floor orbottom, and a top. The enclosure defines a limited amount of spacearound the vessel, between the outside of the vessel and the inside ofthe enclosure, that space being referred to herein as an “interspace.”While the enclosure is substantially closed, it also includes at leasttwo air circulating passages (e.g., an inlet and an outlet) in thewalls, floor, or bottom of the enclosure that allow for a useful flow ofor another ambient gas to be passed into, through, and out of theinterspace. The air circulating passages are of a size and placementthat allow for a useful volume of air (or another ambient gas) to becaused to flow into the enclosure, through the interspace, and out ofthe enclosure, with the volumetric flow of the air being sufficient toremoving a desired amount of heat from the vessel to reduce thetemperature of the vessel and its contents at a desired rate oftemperature reduction.

The air flow through the interspace can be “forced” or “non-convective.”For example, a mechanical impetus, e.g., from a fan or otherair-circulating device, may be used to impart movement of air to causethe air to flow through the interspace. The forced (non-convective) flowof air is different from certain other forms of airflow that may beconsidered convective, passive, or merely incidental (due to themovement of air external to the enclosure), but that may also orotherwise occur in an interspace that contains a heated vessel asdescribed.

In a system or method as described, air flow caused by “convection,”i.e., “convective” air flow, within an interspace, is considered to bemovement (flow) of air within the interspace that results substantiallyor entirely from a temperature and resulting density difference betweenair that is located at or near a surface of a heated vessel within theinterspace, compared to nearby air that is within the interspace butaway from the surface, with the temperature difference being caused bythe transfer of heat energy from the heated vessel to the air that islocated at or near the surface; in this situation, gravity will causeair masses of different temperatures and densities to move within theinterspace. This type of convective air circulation within an interspacecan occur incidentally within a purifier system that is not designed asdescribed herein to use a forced or “non-convective” flow of air throughthe interspace for the specific purpose of absorbing and removing heatenergy from a heated vessel after a regeneration step and during a stepof cooling the interior of the vessel by passing cooling gas through thevessel interior.

As used herein, “non-convective” air flow within an interspace includesthe type of air flow produced by energy being mechanically imparted ontoa volume of air (“mechanically-assisted air movement” or “forced” airmovement), as opposed to the type of air flow that results from air inan interspace absorbing heat energy from a heated vessel; non-convectiveair flow can be produced by energy that is imparted mechanically to airby the use of a fan or other mechanical impeller, so that the air isdirected (drawn or blown) through an inlet of the enclosure, into andthrough the interspace, and then out of the enclosure through an outlet.

The inlet and the outlet are designed and adapted (e.g., in their sizesand locations as part of the enclosure) to specifically accommodate aflow of ambient gas (e.g., air) that has a volume (volumetric flow rate)and temperature (e.g., an ambient temperature) to cause accelerated orrapid cooling of a heated vessel contained in the enclosure, when theambient gas is caused to flowed through the interspace. The source ofmechanical energy (e.g., fan) that causes the non-convective flow can belocated within the enclosure or outside of the enclosure, such as inducting that is a distance away from but in fluid communication with theinterior of the enclosure.

In an apparatus according to the present disclosure, the purificationvessel is substantially contained in a purification vessel enclosurewhich creates an interspace internal to the enclosure and external tothe vessel. The purification vessel enclosure encloses a singlepurification vessel, and is thus distinguished from a purificationsystem housing that may enclose two or more vessels (each also containedin a separate enclosure) and may enclose all or most of an entirepurification system. However, in some embodiments the purificationvessel enclosure may share one or more boundaries with a purificationsystem housing, such as a floor or lower boundary, a ceiling or upperboundary, or one or more walls. The purification vessel enclosure islikewise distinguished from larger enclosures such as a room, building(e.g., factory), or portion of a building, in which the purificationsystem is installed. In some embodiments, the vessel is cylindrical andthe enclosure is rectangular or box-shaped. A clearance distance isgreater at corners of the enclosure and is smaller at locations alongthe wall between the corners. At locations along the wall and betweenthe corners, a minimum distance between the vessel and an enclosure wallmay be 2 inches, one inch, or a half of an inch. For an example vesselthat has a diameter of 36 inches, a distance between the vessel and acorner of the enclosure may be in a range from approximately 26 toapproximately 28 inches; the distance will be comparably greater orsmaller distances for a cylindrical vessel of a greater or smallerdiameter.

The purification vessel enclosure includes at least one enclosure inletto allow for a non-convective flow of ambient atmosphere into theinterspace. The inlet can be connected to ducting and a source ofambient air that can be caused (e.g., by a fan) to flow through theinlet and into the interspace. The ambient air can be taken from anysource of relatively clean air, and need not be purified, and may or maynot be processed by filtering. The air (e.g., “ambient gas”) may besupplied, for example, from a location of a factory that contains thepurifier system but is away from (either near to or distant from,generally) the purifier system, or may alternately be supplied from alocation that is external to the factory. The temperature of the ambientair when introduced to the interspace can be a temperature that is belowthe temperature of the vessel contained in the interspace, e.g., anambient air temperature in a range from 30 to 120 degrees Fahrenheit,such as from 40 or 50 to 75 or 80 degrees Fahrenheit.

A useful or preferred inlet can be of a size to accommodate airflow ofambient air at a flow rate of at least 50 to 400 cubic feet per minute,such as from 100 to 300 cubic feet per minute. An example size of theinlet, i.e., the area of the inlet opening, can be in a range from about7 square inches to about 100 square inches, e.g., from 15 to about 75square inches, and can be opened and closed using a baffle or otherclosure device.

The enclosure inlet may be a single opening, and may optionally andpreferably be adapted to allow for fluid communication with an ambientatmosphere through ducting or another form of fluid conduit. Theenclosure inlet is equipped with an inlet damper to selectively open andclose the enclosure inlet, to selectively allow or prevent a flow of airor another ambient gas through the inlet and into the interspace. Theinlet damper may be capable of operation by hand or by servo, motor,pneumatic actuator, or the like. The inlet damper may be capable ofremote or automated operation, including operation directed by acomputer processing unit. The inlet is distinguished from smalleropenings (e.g., “pass-throughs” as specified hereinabove) that wouldallow for only small and incidental amounts of passive, convectiveairflow.

The purification vessel enclosure includes at least one enclosure outletto allow flow of gas or air out of the interspace into the ambientatmosphere. A useful or preferred outlet can be of a size to accommodateairflow of ambient air at a flow rate of at least 50 to 400 cubic feetper minute, such as from 100 to 300 cubic feet per minute. The size ofthe outlet, i.e., the area of the outlet opening, can be in a range fromabout 7 square inches to about 100 square inches, e.g., from 15 to about75 square inches, and can be opened and closed using a baffle or otherclosure device.

The ambient gas is caused to flow into the interspace through the inletat a positive pressure, meaning a pressure that is greater than anambient pressure at a location external to the enclosure. For example,the ambient gas may enter the enclosure as a gas that has a pressure(measured at the inlet) that is at least 50 torr higher than an ambientpressure, e.g., in a range from 50, 100, or 200 torr, up to 400, 500,600, or 700 torr. The pressure of the ambient gas as the gas flowsthrough the interspace, i.e., the pressure at the interspace, can alsobe greater than the ambient pressure, e.g., at least 20 or 40 torrgreater than the ambient pressure.

The enclosure outlet may be a single opening and may optionally andpreferably communicate with an ambient atmosphere through duct work. Theenclosure outlet is equipped with an outlet damper to selectively openand close the enclosure outlet, to selectively allow or prevent a flowof air out of the interspace. The outlet damper may be capable ofoperation by hand or by servo, motor, pneumatic actuator, or the like.The outlet damper may be capable of remote or automated operation,including operation directed by a computer processing unit.

Different from air circulating passages, the purification vesselenclosure, e.g., at sidewalls, a top, or a bottom, may also optionallybe equipped with small openings (e.g., “pass-throughs”) designed toallow for the passage of various conduits, electrical wiring or cables,fluid-lines, and the like, from an exterior of the enclosure to theinterior, for operating the gas purification system. The enclosurestructure may also include small vents, cracks, or other small openingsthat are not considered to be air circulating passages as describedherein, at least because those types of openings are not designed orused for the purpose of causing a forced (non-convective) flow of airthrough an interspace to reduce the temperature of heated vesselcontained in the enclosure.

The purification vessel enclosure may incidentally serve as a mountingstructure for various conduits, cables, valves, and the like which forma part of the operation of the gas purification system. Desirably, theoutside surface of the purification vessel is in direct contact with airor gas in the interspace so as to allow efficient heat transfer betweenthe outer surface and air or gas that is caused to flow through theinterspace. In such embodiments, the purification vessel is notpartially or wholly covered with any external article such as a heatblanket, insulation blanket, or the like.

In certain useful or preferred example systems, the purification vesselenclosure may be equipped with one or more fans, impellers, or other airmoving apparatus, collectively referred to herein as “fans.” Forexample, the purification vessel enclosure may be equipped with one ormore inlet fans configured to draw ambient gas or air into theinterspace through the enclosure inlet. Alternately or in addition, thepurification vessel enclosure may be equipped with one or more outletfans configured to expel gas or air from the interspace through theenclosure outlet.

Alternately, or in addition, the enclosure may be equipped with one ormore circulation fans at the interior of the enclosure, i.e., within theinterspace, configured to circulate gas or air within the interspace. Invarious embodiments, the purification vessel enclosure may be equippedwith any combination of inlet fans, outlet fans, orinterspace-circulation fans. Such fans may be located within thepurification vessel enclosure, or, in various embodiments, fans orportions thereof maybe located outside the purification vesselenclosure.

In a useful or preferred system, the enclosure may include one or moreheaters, heat exchangers, radiators, or other heat transmittingapparatus, collectively referred to herein as “heaters.” The heater istypically configured so that it may selectively increase the temperatureof gas or air in the interspace within the purification vesselenclosure. The heater may be located at the interior of enclosure, i.e.,within the interspace. In some embodiments, a heater principally taskedwith heating the regeneration gas can be located in or attached to theenclosure so that waste heat escaping the heater may be used to heat thegaseous atmosphere within the interspace. Typically, the heater operatesdirectly on the gas or air within the interspace. Typically, the heaterdoes not operate directly on or contact the purification vessel.

According to the methods described herein, a regeneration processincludes a regeneration step during which a volume of heated fluid iscaused to pass through an interior of a vessel to remove contaminantsfrom filter media contained therein, followed by a cooling step duringwhich fluid is also passed through the vessel interior and filter mediato reduce the temperature of both.

During the regeneration step, valves at the vessel inlet and outlet areoperated to take the vessel off-line relative to manufacturingequipment, and to allow a regeneration gas heated to a regeneration gastemperature to be passed through the purification medium within thepurification vessel. Typical regeneration gas temperatures are in excessof 60 degrees Celsius, often well in excess of 60 degrees Celsius, andmay be in the range from 250 to 450 degrees Celsius. In the operation ofthe apparatus of the present disclosure during a regeneration step, theinlet and the outlet of the enclosure are both closed so that hot air isretained heat within the purification vessel enclosure, i.e., within theinterspace. The hot air at the interspace can contribute toward a highertemperature of the vessel and the filter media in the vessel, therebyreducing the amount of time needed for the regeneration step.Optionally, a circulation fans that is located in the interspace can beturned on during the regeneration step to circulate gas or air in theinterspace, for more even temperature distribution around thepurification vessel, which may also reduce the amount of time requiredfor a regeneration step. Optionally, a heater contained within theinterspace can also be turned on during the regeneration step toincrease the temperature of gas or air in the interspace, and therebyspeed regeneration.

During the cooling step, a cooling gas at a cooling gas temperature ispassed through the purification medium within the purification vessel toassist in cooling. The temperature of the cooling gas (the “cooling gastemperature”) is below the temperature of the vessel or its containedfilter media. Typical cooling gas temperatures are between 10 degreesCelsius and 40 degrees Celsius, e.g., from 10 to 20, 25, or 30 degreesCelsius. The regenerated purification vessel cannot be brought back online until it has cooled to an appropriate purification temperature,such as below about 40 or 30 degrees Celsius, for example to atemperature in a range from 20 to 25 or 20 to 30 degrees Celsius.

In the operation of the apparatus of the present disclosure, both of theinlet damper and the outlet damper are opened during the cooling step toallow ambient gas (e.g., ambient air) at an ambient gas temperature,from an ambient atmosphere, to enter the interspace and to flow throughthe interspace to remove heat from the interspace and the vessel, whichcan preferably reduce the amount of time required for a cooling step.The ambient gas temperature should be below the temperature of thevessel being cooled. Typical ambient gas temperatures can be between 10degrees Celsius and 30 degrees Celsius, e.g., from 10 to 20, 25, or 30degrees Celsius.

Optionally, a circulation fans can be turned on during the cooling stepto cause gas or air to circulate in the interspace. Optionally, a fan atthe inlet, at the outlet, or both, are turned on during the cooling stepto draw ambient gas or air into the interspace, cause the air to passthrough the interspace, and then cause the air to flow from theinterspace through the outlet. Typically, any heater within theinterspace is turned off during the cooling step.

One embodiment of an on-site purification system according to thepresent disclosure is presented at FIG. 1. A first bulk gas source 420,such as a tank, contains a supply of a high purity specialty gas (e.g.,“clean dry air”) that is useful in a clean room manufacturing system. Asecond bulk gas source 425 contains a supply of a second high purityspecialty gas, e.g., one that may be useful in electronic semiconductorproduction, for example hydrogen, argon, helium, oxygen, carbon dioxide,nitrogen, or ammonia (NH₃). Bulk gas sources 420, 425 may be locatedexternal to factory building 800. The bulk gases are supplied topurification systems 500, 510 through conduits 430, 435. Purified cleandry air is supplied to clean rooms 600, 601, 602, 603 through conduits550. Purified specialty gasses are supplied to work stations 700, 701,702, 703 through conduits 560. Purification systems 500, 510 operatecentrally, delivering multiple gasses to multiple destinations within amanufacturing facility.

With reference to FIG. 2, a portion of one embodiment of a gaspurification system 10 according to the present disclosure is depicted.Gas purification system 10 includes purification vessels 110 and 310.First purification vessel 110 is substantially enclosed on all sides infirst purification vessel enclosure 120, which creates first interspace130 internal to first purification vessel enclosure 120 and external tofirst purification vessel 110. Likewise second purification vessel 310is substantially enclosed on all sides in second purification vesselenclosure 320, which creates second interspace 330 internal to secondpurification vessel enclosure 120 and external to second purificationvessel 110.

Purification system housing 15 is external to first purification vesselenclosure 120 and second purification vessel enclosure 320.

The interior of each purification vessel 110, 310 contains purificationmedia (not shown). The interior of each purification vessel 110, 310 isaccessed by vessel inlet conduits 150, 350 and vessel outlet conduits140, 340. During a purification process, i.e., a process of purifying abulk process gas for use in a manufacturing step, vessel inlet valves152, 352 may be used to select input from a bulk process gas source (notshown) through bulk process gas inlet conduits 154, 354. During aregeneration process, vessel inlet valves 152, 352 may be used to selectinput from a regeneration gas source (not shown) through regenerationgas inlet conduits 156, 356.

Regeneration gas is heated to a regeneration gas temperature by passingthe regeneration gas through a regeneration gas heater 190, 390.Regeneration gas heaters 190, 390 are located internal to purificationvessel enclosures 120, 320 (as shown), i.e., at the interspace 130, 330,but may alternately be located external to purification vesselenclosures 120, 320 (not as shown). During the purification process,vessel outlet valves 142, 342 may be used to select output to a purifiedbulk process gas distribution system (not shown) through purified bulkprocess gas outlet conduits 144, 344. During a regeneration process,vessel outlet valves 142, 342 may be used to select output to aregeneration gas destination (not shown), through regeneration gasoutlet conduits 146, 346. Depending on the type of regeneration gasused, the regeneration gas destination may be to storage, sequestration,or release to the atmosphere. During typical operation, only one ofpurification vessels 110, 310 is regenerated at any one time, duringwhich time the other is typically engaged in a purification process.

Purification vessel enclosures 120, 320 include enclosure inlets 160,360, which may be opened or closed using inlet dampers 165, 365, andenclosure outlets 170, 370, which may be opened or closed using outletdampers 175, 375. Purification vessel enclosures 120, 320 may optionallyinclude circulation fans 180, 380. Purification vessel enclosures 120,320 may optionally include heaters 190, 390. During the regenerationstep of the regeneration process, which is typically performed for onlyone vessel at any one time, inlet dampers 165, 365 and outlet dampers175, 375 are closed. Circulation fans 180, 380 may be turned on.Regeneration gas heaters 190, 390 are turned on. During the cooling stepof the regeneration process, inlet dampers 165, 365 and outlet dampers175, 375 are opened. Circulation fans 180, 380 may be turned on.Regeneration gas heaters 190, 390 are turned off.

With reference to FIG. 3A, during the purification process, vessel inletvalve 152 is used to select input from a bulk process gas source (notshown) through bulk process gas inlet conduit 154 and deliver the gas ata purification gas temperature to the interior of purification vessel110 through vessel inlet conduit 150. Purified gas exits purificationvessel 110 through vessel outlet conduit 140. Vessel outlet valve 142 isused to select output to a purified bulk process gas distribution system(not shown) through purified bulk process gas outlet conduits 144. Inletdamper 165 over enclosure inlet 160 and outlet damper 175 over enclosureoutlet 170 may both be opened to allow passive circulation of ambientatmosphere in interspace 130 internal to purification vessel enclosure120.

With reference to FIG. 3B, during the regeneration step of theregeneration process, vessel inlet valve 152 is used to select inputfrom a regeneration gas source (not shown) through regeneration gasinlet conduit 156, which passes through regeneration gas heater 190 tobe heated to a regeneration gas temperature. The regeneration gas isdelivered to the interior of purification vessel 110 through vesselinlet conduit 150. Regeneration gas exits purification vessel 110through vessel outlet conduit 140. Vessel outlet valve 142 is used toselect output to regeneration gas outlet conduit 146. Inlet damper 165over enclosure inlet 160 and outlet damper 175 over enclosure outlet 170are closed to retain heat in interspace 130 internal to purificationvessel enclosure 120. Circulation fan 180 is turned on to distributeheat in interspace 130.

With reference to FIG. 3C, during the cooling step of the regenerationprocess, vessel inlet valve 152 is used to select input from a coolinggas source (not shown), which is typically the same source as theregeneration gas source (as depicted), through cooling gas inletconduits 156 at a cooling gas temperature. The cooling gas is deliveredto the interior of purification vessel 110 through vessel inlet conduit150. Cooling gas exits purification vessel 110 through vessel outletconduit 140. Vessel outlet valve 142 is used to select output to coolinggas outlet conduit 146, which is typically the same outlet as theregeneration gas outlet (as depicted). Inlet damper 165 over enclosureinlet 160 and outlet damper 175 over enclosure outlet 170 are open toallow circulation of ambient atmosphere in interspace 130 internal topurification vessel enclosure 120. Circulation fan 180 is turned on todistribute cooling ambient air in interspace 130.

According to certain preferred methods, a cooling step performed by useof a system as described, that includes air circulating passages asdescribed, with the method including passing a forced (non-convective)flow of ambient air through the interspace, can be performed in a timethat is reduced as compared to a comparable (otherwise identical) methodthat does not include the step of passing the forced flow of ambient airthrough the interspace. As one example, the cooling step can be one thatis carried out with a forced flow of ambient air having a temperature of25 degrees Celsius, that reduces the temperature of the purificationmedia to below 60 degrees Celsius, wherein the time required to reducethe temperature of the purification media to below 60 degrees is lessthan 40, 50, or 60 percent of the time that would be required to reducethe temperature of the purification media to below 60 degrees withoutpassing the ambient air at an ambient air cooling temperature throughthe interspace.

Various modifications and alterations of this disclosure will becomeapparent to those skilled in the art without departing from the scopeand principles of this disclosure, and it should be understood that thisdisclosure is not to be unduly limited to the illustrative embodimentsset forth hereinabove.

The invention claimed is:
 1. A bulk process gas purifier systemcomprising: a purifier comprising a vessel having a vessel interior thatcontains purification media, an enclosure that encloses the vessel anddefines an interspace that is inside the enclosure and external to thevessel, air circulating passages in the enclosure to allow: a flow ofambient gas into the interspace at a positive input pressure;non-convective circulation of the ambient gas within the interspace; andflow of circulated ambient gas from the interspace to an exterior of theenclosure at a positive outlet pressure; the air circulating passagescomprising: an enclosure inlet that allows a flow of ambient gas at apositive input pressure from the exterior of the enclosure into theinterspace; an enclosure outlet that allows a flow of ambient gas at apositive output pressure from the interspace to an exterior of theenclosure; and a bulk process gas circulating system adapted to causethe bulk process gas to flow into the vessel interior, through thepurification media, and out of the vessel interior.
 2. The bulk processgas purifier system according to claim 1 wherein the enclosure inlet hasan opening area of at least 7 square inches.
 3. The bulk process gaspurifier system according to claim 1 wherein the enclosure outlet has anopening area of at least 7 square inches.
 4. The bulk process gaspurifier system according to claim 1 wherein the enclosure inlet isadapted to receive attachment of inlet ductwork.
 5. The bulk process gaspurifier system according to claim 1 wherein the enclosure outlet isadapted to receive attachment of outlet ductwork.
 6. The bulk processgas purifier system according to claim 1 additionally comprising aninlet damper to open and close the enclosure inlet.
 7. The bulk processgas purifier system according to claim 6 wherein the inlet damper isequipped with an inlet actuator capable of opening or closing the inletdamper.
 8. The bulk process gas purifier system according to claim 1additionally comprising an outlet damper to open and close the enclosureoutlet.
 9. The bulk process gas purifier system according to claim 1additionally comprising a circulation fan comprising an impeller locatedwithin the interspace to circulate a gaseous fluid within theinterspace.
 10. The bulk process gas purifier system according to claim1 wherein the enclosure comprises no opening with an opening area of 10cm² or more other than the enclosure inlet and the enclosure outlet,wherein the opening area of a pass-through is measured with any itemspassing through the pass-through in place.
 11. The bulk process gaspurifier system according to claim 1 wherein the enclosure inlet islocated on a top panel of the enclosure and the enclosure outlet islocated on a top panel of the enclosure.
 12. The bulk process gaspurifier system according to claim 1 wherein the positive input pressureexceeds an ambient pressure outside the enclosure by at least 50 torr.13. The bulk process gas purifier system according to claim 1 whereinthe interspace has a positive pressure that exceeds an ambient pressureoutside the enclosure by at least 20 torr.
 14. The bulk process gaspurifier system according to claim 1 wherein the bulk process gascirculating system comprises a heater capable of heating the bulkprocess gas before the bulk gas flows into the vessel interior.
 15. Thebulk process gas purifier system according to claim 1 wherein the bulkprocess gas circulating system includes: a vessel inlet that leadssupply bulk process gas to the vessel, and a vessel outlet that leadspurified bulk process gas from the vessel after passing through thefiltration medium.
 16. The bulk process gas purifier system according toclaim 1 additionally comprising: a second purifier comprising a secondvessel having a second vessel interior that contains second purificationmedia, a second enclosure that encloses the second vessel and defines asecond interspace that is inside the second enclosure and external tothe second vessel, second air circulating passages in the secondenclosure to allow: a flow of ambient gas into the second interspace ata second positive input pressure; non-convective circulation of theambient gas within the second interspace; and flow of circulated ambientgas from the second interspace to an exterior of the second enclosure ata second positive outlet pressure; the second air circulating passagescomprising: a second enclosure inlet that allows a second flow ofambient gas at a second positive input pressure from the exterior of thesecond enclosure into the second interspace; a second enclosure outletthat allows a flow of ambient gas at a second positive output pressurefrom the second interspace to an exterior of the second enclosure; and asecond bulk process gas circulating system adapted to cause the bulkprocess gas to flow into the second vessel interior, through the secondpurification media, and out of the second vessel interior.